1. Field of the Invention
The present invention relates to a molding machine, a clamping system, a burr detection method, and an abnormality detection method.
2. Description of the Related Art
In a molding machine for example a die cast machine, sometimes the melt sprays out from the mating surfaces of the mold resulting in burrs. Various techniques for detecting such burrs have been proposed. Burrs occur due to for example the presence of foreign matter at the mating surfaces of the mold or due to a mold opening force due to the pressure of the melt injected and filled into the cavity of the mold locally exceeding the clamping force.
Japanese Patent Publication (B2) No. 1-55069 discloses technology for detecting occurrence of a burr by comparing an amount of extension of a tie bar at the time of a completion of the clamping and the amount of extension of the tie bar at the time of the completion of the injection.
Further, in a clamping system used in a molding machine for example a die cast machine, any foreign matter existing between the mold parts induces damage to the mold and the formation of burrs. Therefore, various art for detecting the foreign matter have been proposed.
Japanese Patent No. 3245311 judges existence of any foreign matter based on position detection of a moving mold plate. Namely, when there is no foreign matter between a fixed mold plate and the moving mold plate, the moving mold plate can move up to a previously determined mold contact position with a predetermined drive force, but when there is foreign matter, the moving mold plate cannot contact the fixed mold plate and accordingly the moving mold plate cannot move up to the mold contact position. Therefore, existence of any foreign matter is judged according to whether or not the position of the moving mold plate detected by a detector reaches the mold contact position.
In Japanese Patent Publication (B2) No. 1-55069, the tie bars are completely fixed to the fixed mold plate. The amount of extension of a tie bar is detected at the end of the tie bar fixed to the fixed mold plate. Namely, a strain gauge etc. is used to detect the amount of extension at a portion of the tie bar. On the other hand, a tie bar changes in amount of extension corresponding to the thickness of the burr over the entire length between the moving mold plate and the fixed mold plate. Accordingly, Japanese Patent Publication (B2) No. 1-55069 detects only the part corresponding to the thickness of the burr. The detector of the amount of extension must consequently be configured by high precision components. Note that in the clamping system of Japanese Patent Publication (B2) No. 1-55069, the tie bars are completely fixed to the fixed mold plate, therefore the system is considered to be a toggle type clamping system.
Japanese Patent No. 3245311 measures the position of the moving mold plate at one location. On the other hand, the moving mold plate and the fixed mold plate sometimes are not kept parallel due to mechanical error etc. In this case, one edge side of the mating surface of the moving mold plate contacts the mating surface of the fixed mold plate earlier than the other edge side. Further, even after the mold parts contact, sometimes only one edge side contacts the mating surface and the other edge side does not contact it. Accordingly, when detecting the position of the moving mold plate at the contacting edge side, irrespective of the presence of foreign matter in a clearance between the mold parts at the edge side where the mold parts do not contact, it ends up being judged that the detected position has reached the contact position and there is no foreign matter. In other words, in the art of Japanese Patent No. 3245311, sometimes foreign matter cannot be detected over a wide range of the mold mating surfaces.
As described above, conventionally, the positions of a plurality of tie bars have not been detected and the detection results effectively utilized.